kernel/kfifo.c - maze/linux - Git at Google

 /*
  * A generic kernel FIFO implementation.
  *
  * Copyright (C) 2009 Stefani Seibold <stefani@seibold.net>
  * Copyright (C) 2004 Stelian Pop <stelian@popies.net>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  *
  */

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/err.h>
 #include <linux/kfifo.h>
 #include <linux/log2.h>
 #include <linux/uaccess.h>

 static void _kfifo_init(struct kfifo *fifo, void *buffer,
 		unsigned int size)
 {
 	fifo->buffer = buffer;
 	fifo->size = size;

 	kfifo_reset(fifo);
 }

 /**
  * kfifo_init - initialize a FIFO using a preallocated buffer
  * @fifo: the fifo to assign the buffer
  * @buffer: the preallocated buffer to be used.
  * @size: the size of the internal buffer, this has to be a power of 2.
  *
  */
 void kfifo_init(struct kfifo *fifo, void *buffer, unsigned int size)
 {
 	/* size must be a power of 2 */
 	BUG_ON(!is_power_of_2(size));

 	_kfifo_init(fifo, buffer, size);
 }
 EXPORT_SYMBOL(kfifo_init);

 /**
  * kfifo_alloc - allocates a new FIFO internal buffer
  * @fifo: the fifo to assign then new buffer
  * @size: the size of the buffer to be allocated, this have to be a power of 2.
  * @gfp_mask: get_free_pages mask, passed to kmalloc()
  *
  * This function dynamically allocates a new fifo internal buffer
  *
  * The size will be rounded-up to a power of 2.
  * The buffer will be release with kfifo_free().
  * Return 0 if no error, otherwise the an error code
  */
 int kfifo_alloc(struct kfifo *fifo, unsigned int size, gfp_t gfp_mask)
 {
 	unsigned char *buffer;

 	/*
 	 * round up to the next power of 2, since our 'let the indices
 	 * wrap' technique works only in this case.
 	 */
 	if (!is_power_of_2(size)) {
 		BUG_ON(size > 0x80000000);
 		size = roundup_pow_of_two(size);
 	}

 	buffer = kmalloc(size, gfp_mask);
 	if (!buffer) {
 		_kfifo_init(fifo, 0, 0);
 		return -ENOMEM;
 	}

 	_kfifo_init(fifo, buffer, size);

 	return 0;
 }
 EXPORT_SYMBOL(kfifo_alloc);

 /**
  * kfifo_free - frees the FIFO internal buffer
  * @fifo: the fifo to be freed.
  */
 void kfifo_free(struct kfifo *fifo)
 {
 	kfree(fifo->buffer);
 }
 EXPORT_SYMBOL(kfifo_free);

 /**
  * kfifo_skip - skip output data
  * @fifo: the fifo to be used.
  * @len: number of bytes to skip
  */
 void kfifo_skip(struct kfifo *fifo, unsigned int len)
 {
 	if (len < kfifo_len(fifo)) {
 		__kfifo_add_out(fifo, len);
 		return;
 	}
 	kfifo_reset_out(fifo);
 }
 EXPORT_SYMBOL(kfifo_skip);

 static inline void __kfifo_in_data(struct kfifo *fifo,
 		const void *from, unsigned int len, unsigned int off)
 {
 	unsigned int l;

 	/*
 	 * Ensure that we sample the fifo->out index -before- we
 	 * start putting bytes into the kfifo.
 	 */

 	smp_mb();

 	off = __kfifo_off(fifo, fifo->in + off);

 	/* first put the data starting from fifo->in to buffer end */
 	l = min(len, fifo->size - off);
 	memcpy(fifo->buffer + off, from, l);

 	/* then put the rest (if any) at the beginning of the buffer */
 	memcpy(fifo->buffer, from + l, len - l);
 }

 static inline void __kfifo_out_data(struct kfifo *fifo,
 		void *to, unsigned int len, unsigned int off)
 {
 	unsigned int l;

 	/*
 	 * Ensure that we sample the fifo->in index -before- we
 	 * start removing bytes from the kfifo.
 	 */

 	smp_rmb();

 	off = __kfifo_off(fifo, fifo->out + off);

 	/* first get the data from fifo->out until the end of the buffer */
 	l = min(len, fifo->size - off);
 	memcpy(to, fifo->buffer + off, l);

 	/* then get the rest (if any) from the beginning of the buffer */
 	memcpy(to + l, fifo->buffer, len - l);
 }

 static inline int __kfifo_from_user_data(struct kfifo *fifo,
 	 const void __user *from, unsigned int len, unsigned int off,
 	 unsigned *lenout)
 {
 	unsigned int l;
 	int ret;

 	/*
 	 * Ensure that we sample the fifo->out index -before- we
 	 * start putting bytes into the kfifo.
 	 */

 	smp_mb();

 	off = __kfifo_off(fifo, fifo->in + off);

 	/* first put the data starting from fifo->in to buffer end */
 	l = min(len, fifo->size - off);
 	ret = copy_from_user(fifo->buffer + off, from, l);
 	if (unlikely(ret)) {
 		*lenout = ret;
 		return -EFAULT;
 	}
 	*lenout = l;

 	/* then put the rest (if any) at the beginning of the buffer */
 	ret = copy_from_user(fifo->buffer, from + l, len - l);
 	*lenout += ret ? ret : len - l;
 	return ret ? -EFAULT : 0;
 }

 static inline int __kfifo_to_user_data(struct kfifo *fifo,
 		void __user *to, unsigned int len, unsigned int off, unsigned *lenout)
 {
 	unsigned int l;
 	int ret;

 	/*
 	 * Ensure that we sample the fifo->in index -before- we
 	 * start removing bytes from the kfifo.
 	 */

 	smp_rmb();

 	off = __kfifo_off(fifo, fifo->out + off);

 	/* first get the data from fifo->out until the end of the buffer */
 	l = min(len, fifo->size - off);
 	ret = copy_to_user(to, fifo->buffer + off, l);
 	*lenout = l;
 	if (unlikely(ret)) {
 		*lenout -= ret;
 		return -EFAULT;
 	}

 	/* then get the rest (if any) from the beginning of the buffer */
 	len -= l;
 	ret = copy_to_user(to + l, fifo->buffer, len);
 	if (unlikely(ret)) {
 		*lenout += len - ret;
 		return -EFAULT;
 	}
 	*lenout += len;
 	return 0;
 }

 unsigned int __kfifo_in_n(struct kfifo *fifo,
 	const void *from, unsigned int len, unsigned int recsize)
 {
 	if (kfifo_avail(fifo) < len + recsize)
 		return len + 1;

 	__kfifo_in_data(fifo, from, len, recsize);
 	return 0;
 }
 EXPORT_SYMBOL(__kfifo_in_n);

 /**
  * kfifo_in - puts some data into the FIFO
  * @fifo: the fifo to be used.
  * @from: the data to be added.
  * @len: the length of the data to be added.
  *
  * This function copies at most @len bytes from the @from buffer into
  * the FIFO depending on the free space, and returns the number of
  * bytes copied.
  *
  * Note that with only one concurrent reader and one concurrent
  * writer, you don't need extra locking to use these functions.
  */
 unsigned int kfifo_in(struct kfifo *fifo, const void *from,
 				unsigned int len)
 {
 	len = min(kfifo_avail(fifo), len);

 	__kfifo_in_data(fifo, from, len, 0);
 	__kfifo_add_in(fifo, len);
 	return len;
 }
 EXPORT_SYMBOL(kfifo_in);

 unsigned int __kfifo_in_generic(struct kfifo *fifo,
 	const void *from, unsigned int len, unsigned int recsize)
 {
 	return __kfifo_in_rec(fifo, from, len, recsize);
 }
 EXPORT_SYMBOL(__kfifo_in_generic);

 unsigned int __kfifo_out_n(struct kfifo *fifo,
 	void *to, unsigned int len, unsigned int recsize)
 {
 	if (kfifo_len(fifo) < len + recsize)
 		return len;

 	__kfifo_out_data(fifo, to, len, recsize);
 	__kfifo_add_out(fifo, len + recsize);
 	return 0;
 }
 EXPORT_SYMBOL(__kfifo_out_n);

 /**
  * kfifo_out - gets some data from the FIFO
  * @fifo: the fifo to be used.
  * @to: where the data must be copied.
  * @len: the size of the destination buffer.
  *
  * This function copies at most @len bytes from the FIFO into the
  * @to buffer and returns the number of copied bytes.
  *
  * Note that with only one concurrent reader and one concurrent
  * writer, you don't need extra locking to use these functions.
  */
 unsigned int kfifo_out(struct kfifo *fifo, void *to, unsigned int len)
 {
 	len = min(kfifo_len(fifo), len);

 	__kfifo_out_data(fifo, to, len, 0);
 	__kfifo_add_out(fifo, len);

 	return len;
 }
 EXPORT_SYMBOL(kfifo_out);

 /**
  * kfifo_out_peek - copy some data from the FIFO, but do not remove it
  * @fifo: the fifo to be used.
  * @to: where the data must be copied.
  * @len: the size of the destination buffer.
  * @offset: offset into the fifo
  *
  * This function copies at most @len bytes at @offset from the FIFO
  * into the @to buffer and returns the number of copied bytes.
  * The data is not removed from the FIFO.
  */
 unsigned int kfifo_out_peek(struct kfifo *fifo, void *to, unsigned int len,
 			    unsigned offset)
 {
 	len = min(kfifo_len(fifo), len + offset);

 	__kfifo_out_data(fifo, to, len, offset);
 	return len;
 }
 EXPORT_SYMBOL(kfifo_out_peek);

 unsigned int __kfifo_out_generic(struct kfifo *fifo,
 	void *to, unsigned int len, unsigned int recsize,
 	unsigned int *total)
 {
 	return __kfifo_out_rec(fifo, to, len, recsize, total);
 }
 EXPORT_SYMBOL(__kfifo_out_generic);

 unsigned int __kfifo_from_user_n(struct kfifo *fifo,
 	const void __user *from, unsigned int len, unsigned int recsize)
 {
 	unsigned total;

 	if (kfifo_avail(fifo) < len + recsize)
 		return len + 1;

 	__kfifo_from_user_data(fifo, from, len, recsize, &total);
 	return total;
 }
 EXPORT_SYMBOL(__kfifo_from_user_n);

 /**
  * kfifo_from_user - puts some data from user space into the FIFO
  * @fifo: the fifo to be used.
  * @from: pointer to the data to be added.
  * @len: the length of the data to be added.
  *
  * This function copies at most @len bytes from the @from into the
  * FIFO depending and returns -EFAULT/0.
  *
  * Note that with only one concurrent reader and one concurrent
  * writer, you don't need extra locking to use these functions.
  */
 int kfifo_from_user(struct kfifo *fifo,
         const void __user *from, unsigned int len, unsigned *total)
 {
 	int ret;
 	len = min(kfifo_avail(fifo), len);
 	ret = __kfifo_from_user_data(fifo, from, len, 0, total);
 	if (ret)
 		return ret;
 	__kfifo_add_in(fifo, len);
 	return 0;
 }
 EXPORT_SYMBOL(kfifo_from_user);

 unsigned int __kfifo_from_user_generic(struct kfifo *fifo,
 	const void __user *from, unsigned int len, unsigned int recsize)
 {
 	return __kfifo_from_user_rec(fifo, from, len, recsize);
 }
 EXPORT_SYMBOL(__kfifo_from_user_generic);

 unsigned int __kfifo_to_user_n(struct kfifo *fifo,
 	void __user *to, unsigned int len, unsigned int reclen,
 	unsigned int recsize)
 {
 	unsigned int ret, total;

 	if (kfifo_len(fifo) < reclen + recsize)
 		return len;

 	ret = __kfifo_to_user_data(fifo, to, reclen, recsize, &total);

 	if (likely(ret == 0))
 		__kfifo_add_out(fifo, reclen + recsize);

 	return total;
 }
 EXPORT_SYMBOL(__kfifo_to_user_n);

 /**
  * kfifo_to_user - gets data from the FIFO and write it to user space
  * @fifo: the fifo to be used.
  * @to: where the data must be copied.
  * @len: the size of the destination buffer.
  @ @lenout: pointer to output variable with copied data
  *
  * This function copies at most @len bytes from the FIFO into the
  * @to buffer and 0 or -EFAULT.
  *
  * Note that with only one concurrent reader and one concurrent
  * writer, you don't need extra locking to use these functions.
  */
 int kfifo_to_user(struct kfifo *fifo,
 	void __user *to, unsigned int len, unsigned *lenout)
 {
 	int ret;
 	len = min(kfifo_len(fifo), len);
 	ret = __kfifo_to_user_data(fifo, to, len, 0, lenout);
 	__kfifo_add_out(fifo, *lenout);
 	return ret;
 }
 EXPORT_SYMBOL(kfifo_to_user);

 unsigned int __kfifo_to_user_generic(struct kfifo *fifo,
 	void __user *to, unsigned int len, unsigned int recsize,
 	unsigned int *total)
 {
 	return __kfifo_to_user_rec(fifo, to, len, recsize, total);
 }
 EXPORT_SYMBOL(__kfifo_to_user_generic);

 unsigned int __kfifo_peek_generic(struct kfifo *fifo, unsigned int recsize)
 {
 	if (recsize == 0)
 		return kfifo_avail(fifo);

 	return __kfifo_peek_n(fifo, recsize);
 }
 EXPORT_SYMBOL(__kfifo_peek_generic);

 void __kfifo_skip_generic(struct kfifo *fifo, unsigned int recsize)
 {
 	__kfifo_skip_rec(fifo, recsize);
 }
 EXPORT_SYMBOL(__kfifo_skip_generic);
	/*
	* A generic kernel FIFO implementation.
	*
	* Copyright (C) 2009 Stefani Seibold <stefani@seibold.net>
	* Copyright (C) 2004 Stelian Pop <stelian@popies.net>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
	*
	*/

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/slab.h>
	#include <linux/err.h>
	#include <linux/kfifo.h>
	#include <linux/log2.h>
	#include <linux/uaccess.h>

	static void _kfifo_init(struct kfifo fifo, void buffer,
	unsigned int size)
	{
	fifo->buffer = buffer;
	fifo->size = size;

	kfifo_reset(fifo);
	}

	/**
	* kfifo_init - initialize a FIFO using a preallocated buffer
	* @fifo: the fifo to assign the buffer
	* @buffer: the preallocated buffer to be used.
	* @size: the size of the internal buffer, this has to be a power of 2.
	*
	*/
	void kfifo_init(struct kfifo fifo, void buffer, unsigned int size)
	{
	/* size must be a power of 2 */
	BUG_ON(!is_power_of_2(size));

	_kfifo_init(fifo, buffer, size);
	}
	EXPORT_SYMBOL(kfifo_init);

	/**
	* kfifo_alloc - allocates a new FIFO internal buffer
	* @fifo: the fifo to assign then new buffer
	* @size: the size of the buffer to be allocated, this have to be a power of 2.
	* @gfp_mask: get_free_pages mask, passed to kmalloc()
	*
	* This function dynamically allocates a new fifo internal buffer
	*
	* The size will be rounded-up to a power of 2.
	* The buffer will be release with kfifo_free().
	* Return 0 if no error, otherwise the an error code
	*/
	int kfifo_alloc(struct kfifo *fifo, unsigned int size, gfp_t gfp_mask)
	{
	unsigned char *buffer;

	/*
	* round up to the next power of 2, since our 'let the indices
	* wrap' technique works only in this case.
	*/
	if (!is_power_of_2(size)) {
	BUG_ON(size > 0x80000000);
	size = roundup_pow_of_two(size);
	}

	buffer = kmalloc(size, gfp_mask);
	if (!buffer) {
	_kfifo_init(fifo, 0, 0);
	return -ENOMEM;
	}

	_kfifo_init(fifo, buffer, size);

	return 0;
	}
	EXPORT_SYMBOL(kfifo_alloc);

	/**
	* kfifo_free - frees the FIFO internal buffer
	* @fifo: the fifo to be freed.
	*/
	void kfifo_free(struct kfifo *fifo)
	{
	kfree(fifo->buffer);
	}
	EXPORT_SYMBOL(kfifo_free);

	/**
	* kfifo_skip - skip output data
	* @fifo: the fifo to be used.
	* @len: number of bytes to skip
	*/
	void kfifo_skip(struct kfifo *fifo, unsigned int len)
	{
	if (len < kfifo_len(fifo)) {
	__kfifo_add_out(fifo, len);
	return;
	}
	kfifo_reset_out(fifo);
	}
	EXPORT_SYMBOL(kfifo_skip);

	static inline void __kfifo_in_data(struct kfifo *fifo,
	const void *from, unsigned int len, unsigned int off)
	{
	unsigned int l;

	/*
	* Ensure that we sample the fifo->out index -before- we
	* start putting bytes into the kfifo.
	*/

	smp_mb();

	off = __kfifo_off(fifo, fifo->in + off);

	/* first put the data starting from fifo->in to buffer end */
	l = min(len, fifo->size - off);
	memcpy(fifo->buffer + off, from, l);

	/* then put the rest (if any) at the beginning of the buffer */
	memcpy(fifo->buffer, from + l, len - l);
	}

	static inline void __kfifo_out_data(struct kfifo *fifo,
	void *to, unsigned int len, unsigned int off)
	{
	unsigned int l;

	/*
	* Ensure that we sample the fifo->in index -before- we
	* start removing bytes from the kfifo.
	*/

	smp_rmb();

	off = __kfifo_off(fifo, fifo->out + off);

	/* first get the data from fifo->out until the end of the buffer */
	l = min(len, fifo->size - off);
	memcpy(to, fifo->buffer + off, l);

	/* then get the rest (if any) from the beginning of the buffer */
	memcpy(to + l, fifo->buffer, len - l);
	}

	static inline int __kfifo_from_user_data(struct kfifo *fifo,
	const void __user *from, unsigned int len, unsigned int off,
	unsigned *lenout)
	{
	unsigned int l;
	int ret;

	/*
	* Ensure that we sample the fifo->out index -before- we
	* start putting bytes into the kfifo.
	*/

	smp_mb();

	off = __kfifo_off(fifo, fifo->in + off);

	/* first put the data starting from fifo->in to buffer end */
	l = min(len, fifo->size - off);
	ret = copy_from_user(fifo->buffer + off, from, l);
	if (unlikely(ret)) {
	*lenout = ret;
	return -EFAULT;
	}
	*lenout = l;

	/* then put the rest (if any) at the beginning of the buffer */
	ret = copy_from_user(fifo->buffer, from + l, len - l);
	*lenout += ret ? ret : len - l;
	return ret ? -EFAULT : 0;
	}

	static inline int __kfifo_to_user_data(struct kfifo *fifo,
	void __user to, unsigned int len, unsigned int off, unsigned lenout)
	{
	unsigned int l;
	int ret;

	/*
	* Ensure that we sample the fifo->in index -before- we
	* start removing bytes from the kfifo.
	*/

	smp_rmb();

	off = __kfifo_off(fifo, fifo->out + off);

	/* first get the data from fifo->out until the end of the buffer */
	l = min(len, fifo->size - off);
	ret = copy_to_user(to, fifo->buffer + off, l);
	*lenout = l;
	if (unlikely(ret)) {
	*lenout -= ret;
	return -EFAULT;
	}

	/* then get the rest (if any) from the beginning of the buffer */
	len -= l;
	ret = copy_to_user(to + l, fifo->buffer, len);
	if (unlikely(ret)) {
	*lenout += len - ret;
	return -EFAULT;
	}
	*lenout += len;
	return 0;
	}

	unsigned int __kfifo_in_n(struct kfifo *fifo,
	const void *from, unsigned int len, unsigned int recsize)
	{
	if (kfifo_avail(fifo) < len + recsize)
	return len + 1;

	__kfifo_in_data(fifo, from, len, recsize);
	return 0;
	}
	EXPORT_SYMBOL(__kfifo_in_n);

	/**
	* kfifo_in - puts some data into the FIFO
	* @fifo: the fifo to be used.
	* @from: the data to be added.
	* @len: the length of the data to be added.
	*
	* This function copies at most @len bytes from the @from buffer into
	* the FIFO depending on the free space, and returns the number of
	* bytes copied.
	*
	* Note that with only one concurrent reader and one concurrent
	* writer, you don't need extra locking to use these functions.
	*/
	unsigned int kfifo_in(struct kfifo fifo, const void from,
	unsigned int len)
	{
	len = min(kfifo_avail(fifo), len);

	__kfifo_in_data(fifo, from, len, 0);
	__kfifo_add_in(fifo, len);
	return len;
	}
	EXPORT_SYMBOL(kfifo_in);

	unsigned int __kfifo_in_generic(struct kfifo *fifo,
	const void *from, unsigned int len, unsigned int recsize)
	{
	return __kfifo_in_rec(fifo, from, len, recsize);
	}
	EXPORT_SYMBOL(__kfifo_in_generic);

	unsigned int __kfifo_out_n(struct kfifo *fifo,
	void *to, unsigned int len, unsigned int recsize)
	{
	if (kfifo_len(fifo) < len + recsize)
	return len;

	__kfifo_out_data(fifo, to, len, recsize);
	__kfifo_add_out(fifo, len + recsize);
	return 0;
	}
	EXPORT_SYMBOL(__kfifo_out_n);

	/**
	* kfifo_out - gets some data from the FIFO
	* @fifo: the fifo to be used.
	* @to: where the data must be copied.
	* @len: the size of the destination buffer.
	*
	* This function copies at most @len bytes from the FIFO into the
	* @to buffer and returns the number of copied bytes.
	*
	* Note that with only one concurrent reader and one concurrent
	* writer, you don't need extra locking to use these functions.
	*/
	unsigned int kfifo_out(struct kfifo fifo, void to, unsigned int len)
	{
	len = min(kfifo_len(fifo), len);

	__kfifo_out_data(fifo, to, len, 0);
	__kfifo_add_out(fifo, len);

	return len;
	}
	EXPORT_SYMBOL(kfifo_out);

	/**
	* kfifo_out_peek - copy some data from the FIFO, but do not remove it
	* @fifo: the fifo to be used.
	* @to: where the data must be copied.
	* @len: the size of the destination buffer.
	* @offset: offset into the fifo
	*
	* This function copies at most @len bytes at @offset from the FIFO
	* into the @to buffer and returns the number of copied bytes.
	* The data is not removed from the FIFO.
	*/
	unsigned int kfifo_out_peek(struct kfifo fifo, void to, unsigned int len,
	unsigned offset)
	{
	len = min(kfifo_len(fifo), len + offset);

	__kfifo_out_data(fifo, to, len, offset);
	return len;
	}
	EXPORT_SYMBOL(kfifo_out_peek);

	unsigned int __kfifo_out_generic(struct kfifo *fifo,
	void *to, unsigned int len, unsigned int recsize,
	unsigned int *total)
	{
	return __kfifo_out_rec(fifo, to, len, recsize, total);
	}
	EXPORT_SYMBOL(__kfifo_out_generic);

	unsigned int __kfifo_from_user_n(struct kfifo *fifo,
	const void __user *from, unsigned int len, unsigned int recsize)
	{
	unsigned total;

	if (kfifo_avail(fifo) < len + recsize)
	return len + 1;

	__kfifo_from_user_data(fifo, from, len, recsize, &total);
	return total;
	}
	EXPORT_SYMBOL(__kfifo_from_user_n);

	/**
	* kfifo_from_user - puts some data from user space into the FIFO
	* @fifo: the fifo to be used.
	* @from: pointer to the data to be added.
	* @len: the length of the data to be added.
	*
	* This function copies at most @len bytes from the @from into the
	* FIFO depending and returns -EFAULT/0.
	*
	* Note that with only one concurrent reader and one concurrent
	* writer, you don't need extra locking to use these functions.
	*/
	int kfifo_from_user(struct kfifo *fifo,
	const void __user from, unsigned int len, unsigned total)
	{
	int ret;
	len = min(kfifo_avail(fifo), len);
	ret = __kfifo_from_user_data(fifo, from, len, 0, total);
	if (ret)
	return ret;
	__kfifo_add_in(fifo, len);
	return 0;
	}
	EXPORT_SYMBOL(kfifo_from_user);

	unsigned int __kfifo_from_user_generic(struct kfifo *fifo,
	const void __user *from, unsigned int len, unsigned int recsize)
	{
	return __kfifo_from_user_rec(fifo, from, len, recsize);
	}
	EXPORT_SYMBOL(__kfifo_from_user_generic);

	unsigned int __kfifo_to_user_n(struct kfifo *fifo,
	void __user *to, unsigned int len, unsigned int reclen,
	unsigned int recsize)
	{
	unsigned int ret, total;

	if (kfifo_len(fifo) < reclen + recsize)
	return len;

	ret = __kfifo_to_user_data(fifo, to, reclen, recsize, &total);

	if (likely(ret == 0))
	__kfifo_add_out(fifo, reclen + recsize);

	return total;
	}
	EXPORT_SYMBOL(__kfifo_to_user_n);

	/**
	* kfifo_to_user - gets data from the FIFO and write it to user space
	* @fifo: the fifo to be used.
	* @to: where the data must be copied.
	* @len: the size of the destination buffer.
	@ @lenout: pointer to output variable with copied data
	*
	* This function copies at most @len bytes from the FIFO into the
	* @to buffer and 0 or -EFAULT.
	*
	* Note that with only one concurrent reader and one concurrent
	* writer, you don't need extra locking to use these functions.
	*/
	int kfifo_to_user(struct kfifo *fifo,
	void __user to, unsigned int len, unsigned lenout)
	{
	int ret;
	len = min(kfifo_len(fifo), len);
	ret = __kfifo_to_user_data(fifo, to, len, 0, lenout);
	__kfifo_add_out(fifo, *lenout);
	return ret;
	}
	EXPORT_SYMBOL(kfifo_to_user);

	unsigned int __kfifo_to_user_generic(struct kfifo *fifo,
	void __user *to, unsigned int len, unsigned int recsize,
	unsigned int *total)
	{
	return __kfifo_to_user_rec(fifo, to, len, recsize, total);
	}
	EXPORT_SYMBOL(__kfifo_to_user_generic);

	unsigned int __kfifo_peek_generic(struct kfifo *fifo, unsigned int recsize)
	{
	if (recsize == 0)
	return kfifo_avail(fifo);

	return __kfifo_peek_n(fifo, recsize);
	}
	EXPORT_SYMBOL(__kfifo_peek_generic);

	void __kfifo_skip_generic(struct kfifo *fifo, unsigned int recsize)
	{
	__kfifo_skip_rec(fifo, recsize);
	}
	EXPORT_SYMBOL(__kfifo_skip_generic);